1. Field of the Invention
The present invention relates to a thin-film transistor (“TFT”) substrate and a method of repairing the same, and more particularly, to a TFT substrate and a method of repairing the same, in which a defective pixel can be repaired while additional capacitance is substantially reduced and/or effectively prevented.
2. Description of the Related Art
Liquid crystal displays (“LCDs”) are a type of widely-used flat panel display (“FPD”). An LCD typically includes a thin-film transistor (“TFT”) substrate on which gate lines, data lines, pixel electrodes and TFTs, for example, are formed, a color filter substrate on which common electrodes and color filters are formed, a liquid crystal display panel which includes a liquid crystal layer between the TFT substrate and the color filter substrate, and a driver which drives the liquid crystal display panel. In operation, the LCD applies voltages to the pixel electrodes and the common electrodes and thus generates an electric field in the liquid crystal layer therebetween. An alignment of liquid crystal molecules in the liquid crystal layer is controlled by the generated electric field, and the LCD thereby controls a polarization of incident light. As a result, a desired image is displayed on the LCD.
In a manufacturing process, after modules of an LCD are completed, a test pattern is displayed on a liquid crystal display panel to determine whether there are defective pixels present in the liquid crystal display panel. If a defective pixel is detected, it is repaired.
In general, defects found in liquid crystal display panels are classified as spot defects (such as color defects of pixels, bright-spot defects and dark-spot defects) and line defects caused by short circuits between gate lines and adjacent data lines. A dark-spot defect occurs when a region appears dark at a high grayscale level, e.g., in a white state, due to leakage of light. A bright-spot defect occurs when a region appears bright at a low grayscale level, e.g., in a black state, due to leakage of light.
Human eyes are more sensitive to bright-spot defects in a dark state than dark-spot defects in a bright state. Thus, a stricter standard is typically applied when determining whether a liquid crystal display panel has bright-spot defects than when determining whether the liquid crystal display panel has dark-spot defects.
Generally, a bright-spot defect occurs when a conductive material remaining between a data line and a pixel electrode causes an electrical short circuit therebetween, when a short circuit forms between a pixel electrode and a common electrode or when a connection between a pixel electrode and a TFT fails, for example.
To repair bright-spot defects, a protrusion pattern may be formed to protrude from each pixel electrode. In this case, the protrusion pattern has a predetermined width and height and is formed to overlap a preceding gate line. In addition, a protrusion pattern in an LCD of the prior art has a substantially rectangular or square shape of a predetermined size. As a result, a drain electrode of a TFT in a defective cell having a bright-spot defect, for example, may be opened, and a laser beam is irradiated to a protruding portion of a corresponding pixel electrode to form a short circuit between the pixel electrode having the defective cell and an adjacent gate line.
When a protrusion pattern of a pixel electrode is formed to overlap a preceding gate line, as described above, additional capacitance (as well as liquid crystal capacitance and storage capacitance) is created in each pixel. The additional capacitance increases the overall capacitance of each pixel, which, in turn, increases a gate load of the liquid crystal display panel which has been repaired. As a result, a gate signal is delayed, and image quality of the LCD deteriorates.